Eutectic and fusion bonding has been used for MEMS (micro electro mechanical systems) production procedure as a wafer level package process. The eutectic and fusion bonding describes a wafer bonding technique with an intermediate metal layer that may form a eutectic system. The eutectic metals may be alloys that transform directly from solid to liquid state or vice versa from liquid to solid state at a specific temperature without passing a two-phase equilibrium. Moreover, the eutectic temperature is lower than the melting temperature of the two or more pure elements, so that it is convenient to reduce the process temperature of a bonding process between two elements.
For example, when there is a need to bond a wafer to another wafer, the eutectic and fusion bonding process may be used. In general, the bonding process has two main functions: one function is to package the two wafers in wafer level, and the other function is to maintain the pressure of a device of the wafer. Some semiconductor products need precisely optical alignment to make perfect bonding. If the alignment system of a bonding tool used in the bonding process is abnormal, the wafers may be shifted to bond, and thereby leading device vacuum leakage. Since the eutectic bond alignment precision and the process stability are difficultly improved, the yield rate of the products is also difficultly improved.